Containers for pressurized aerosols have traditionally been fabricated from metal sheet due to the need for the container body to withstand the pressures of the aerosol contents. In this regard, accompanying FIG. 1 shows a typical prior art aerosol container C1 which includes a generally tubular metal container body B having its upper edge curled to form a circumferential mounting bead MB that establishes a relatively large mouth opening MO at the body's upper end. The mouth MO is closed with a metal cap C which includes an aerosol dispensing nozzle N of a conventional variety for dispensing the aerosol contents from the container C1. The metal cap C includes a circumferential mounting flange MF that is crimped onto the mounting bead MB of the container body B so as to provide a fluid-tight closure of the mouth opening MO.
Recently, however, resin aerosol containers have be produced by blow-molding techniques. In this regard, please see Japanese Laid-Open Application No. 125470/1978. However, it is difficult to produce containers having uniform thicknesses by conventional blow-molding techniques resulting in poor resistance to the pressure of the container's contents. In addition, the dimensional inaccuracies of the mounting bead at the upper edge of the container body result from blow-molding techniques resulting in inadequate fluid-seals between the dispensing cap and the container body.
In order to overcome the problems associated with the blow-molded aerosol containers, it has been proposed in Japanese Laid-Open Application No. 93482/1986 to form aerosol containers using injection molding techniques. An example of such an injection-molded container is represented container C2 in accompanying FIG. 2. As is seen, this conventional container C2 includes a container body B' formed of a suitable resin material. A lid L, also formed of a suitable resin material, is rigidly attached, for example, via ultrasonic welding techniques, to the upper edge E of the container body B' so as to form a fluid-tight seal therebetween. The upper end of the lid L is formed with a circumferential mounting bead MB'. The metallic dispensing cap C may then be coupled to the lid L by crimping its circumferential mounting flange MF' to the mounting bead MB' so as to close the open end of body B'.
However, it has been found that when containers of the type shown in FIG. 2 are allowed to stand for prolonged periods of time with pressurized contents, the contents occasionally leak therefrom because insufficient seals are formed between the crimped mounting flange MF' of metallic cap C and the mounting bead MB' and/or between the lid L and the upper edge E of the container body B'.
In this regard, it has been found that the radially narrowed mouth MO' defined by the interior surface of the lid L requires that the injection molding gate G be positioned on the mounting bead MB' (see FIG. 3) in order to prevent forced removal of the molded lid L from the mold when it is fabricated. As a result, a burr is usually formed when the solidified residue R associated with the injection molding gate G is removed from the mounting bead MB' thereby increasing the likelihood that an insufficient fluid-tight seal will be established between the mounting flange MF' of cap C and the mounting bead MB'. In addition, removal of such a burr requires that the lid L be subjected to an after-treatment so as to smooth the burr in an attempt to obviate the sealing problems noted above. Of course, such an after-treatment necessarily increases the cost of fabricating the lid L.
One further disadvantage of the resin lid L shown in accompanying FIG. 2 is that, in order to minimize the occurrence of burrs (and also minimize the costs associated with smoothing after-treatments), only a single injection gate is employed during the injection molding operation. However, the dimensional inaccuracies of such a single-gated injection molded lid L usually ensue thereby resulting in improper and/or incomplete fluid seals when the lid L is coupled to the container body B'.
What has been needed in this art, therefore, is an injection molded resin lid of high dimensional accuracy which does not need smoothing after-treatments. It is towards supplying such a need that the present invention is directed.
The present invention is directed to aerosol containers fabricated from injection-moldable resins, whereby the containers include a generally tubular body, ah injection-molded resin lid attached to an upper end of the container body and having a relatively thickened circumferential bead defining an open mouth, and an aerosol dispensing cap sealingly fixed to the bead of the lid and closing the defined open mouth thereof. Broadly, the present invention is especially characterized by providing at least three injection molding gates at a lower interior surface region of the mounting bead, whereby the molding gates are circumferentially spaced-apart from one another at substantially equal intervals.
Further aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.